From: Chaoyi Chen <chaoyi.chen@rock-chips.com>

The HPD function of Type-C DP is implemented through
drm_connector_oob_hotplug_event(). For embedded DP, it is required
that the DRM connector fwnode corresponds to the Type-C port fwnode.

To describe the relationship between the DP controller and the Type-C
port device, we usually using drm_bridge to build a bridge chain.

Now several USB-C controller drivers have already implemented the DP
HPD bridge function provided by aux-hpd-bridge.c, it will build a DP
HPD bridge on USB-C connector port device.

But this requires the USB-C controller driver to manually register the
HPD bridge. If the driver does not implement this feature, the bridge
will not be create.

So this patch implements a generic DP HPD bridge based on
aux-hpd-bridge.c. It will monitor Type-C bus events, and when a
Type-C port device containing the DP svid is registered, it will
create an HPD bridge for it without the need for the USB-C controller
driver to implement it.

Signed-off-by: Chaoyi Chen <chaoyi.chen@rock-chips.com>
---

Changes in v11:
- Switch to using typec bus notifiers.

(no changes since v10)

Changes in v9:
- Remove the exposed DRM_AUX_HPD_BRIDGE option, and select
DRM_AUX_HPD_TYPEC_BRIDGE when it is available.
- Add more commit comment about problem background.

Changes in v8:
- Merge generic DP HPD bridge into one module.

 drivers/gpu/drm/bridge/Kconfig                | 10 ++++
 drivers/gpu/drm/bridge/Makefile               |  1 +
 .../gpu/drm/bridge/aux-hpd-typec-dp-bridge.c  | 51 +++++++++++++++++++
 3 files changed, 62 insertions(+)
 create mode 100644 drivers/gpu/drm/bridge/aux-hpd-typec-dp-bridge.c

diff --git a/drivers/gpu/drm/bridge/Kconfig b/drivers/gpu/drm/bridge/Kconfig
index a250afd8d662..559487aa09a9 100644
--- a/drivers/gpu/drm/bridge/Kconfig
+++ b/drivers/gpu/drm/bridge/Kconfig
@@ -30,6 +30,16 @@ config DRM_AUX_HPD_BRIDGE
 	  Simple bridge that terminates the bridge chain and provides HPD
 	  support.
 
+if DRM_AUX_HPD_BRIDGE
+config DRM_AUX_HPD_TYPEC_BRIDGE
+	tristate
+	depends on TYPEC || !TYPEC
+	default TYPEC
+	help
+	  Simple bridge that terminates the bridge chain and provides HPD
+	  support. It build bridge on each USB-C connector device node.
+endif
+
 menu "Display Interface Bridges"
 	depends on DRM && DRM_BRIDGE
 
diff --git a/drivers/gpu/drm/bridge/Makefile b/drivers/gpu/drm/bridge/Makefile
index c7dc03182e59..a3a0393d2e72 100644
--- a/drivers/gpu/drm/bridge/Makefile
+++ b/drivers/gpu/drm/bridge/Makefile
@@ -1,6 +1,7 @@
 # SPDX-License-Identifier: GPL-2.0
 obj-$(CONFIG_DRM_AUX_BRIDGE) += aux-bridge.o
 obj-$(CONFIG_DRM_AUX_HPD_BRIDGE) += aux-hpd-bridge.o
+obj-$(CONFIG_DRM_AUX_HPD_TYPEC_BRIDGE) += aux-hpd-typec-dp-bridge.o
 obj-$(CONFIG_DRM_CHIPONE_ICN6211) += chipone-icn6211.o
 obj-$(CONFIG_DRM_CHRONTEL_CH7033) += chrontel-ch7033.o
 obj-$(CONFIG_DRM_CROS_EC_ANX7688) += cros-ec-anx7688.o
diff --git a/drivers/gpu/drm/bridge/aux-hpd-typec-dp-bridge.c b/drivers/gpu/drm/bridge/aux-hpd-typec-dp-bridge.c
new file mode 100644
index 000000000000..94be3d5f69e9
--- /dev/null
+++ b/drivers/gpu/drm/bridge/aux-hpd-typec-dp-bridge.c
@@ -0,0 +1,51 @@
+// SPDX-License-Identifier: GPL-2.0+
+#include <linux/of.h>
+#include <linux/usb/typec_altmode.h>
+#include <linux/usb/typec_dp.h>
+
+#include <drm/bridge/aux-bridge.h>
+
+static int drm_typec_bus_event(struct notifier_block *nb,
+			       unsigned long action, void *data)
+{
+	struct device *dev = (struct device *)data;
+	struct typec_altmode *alt = to_typec_altmode(dev);
+
+	if (action != BUS_NOTIFY_ADD_DEVICE)
+		goto done;
+
+	if (is_typec_partner_altmode(&alt->dev) || alt->svid != USB_TYPEC_DP_SID)
+		goto done;
+
+	/*
+	 * alt->dev.parent->parent : USB-C controller device
+	 * alt->dev.parent         : USB-C connector device
+	 */
+	drm_dp_hpd_bridge_register(alt->dev.parent->parent,
+				   to_of_node(alt->dev.parent->fwnode));
+
+done:
+	return NOTIFY_OK;
+}
+
+static struct notifier_block drm_typec_event_nb = {
+	.notifier_call = drm_typec_bus_event,
+};
+
+static void drm_aux_hpd_typec_dp_bridge_module_exit(void)
+{
+	bus_unregister_notifier(&typec_bus, &drm_typec_event_nb);
+}
+
+static int __init drm_aux_hpd_typec_dp_bridge_module_init(void)
+{
+	bus_register_notifier(&typec_bus, &drm_typec_event_nb);
+
+	return 0;
+}
+
+module_init(drm_aux_hpd_typec_dp_bridge_module_init);
+module_exit(drm_aux_hpd_typec_dp_bridge_module_exit);
+
+MODULE_DESCRIPTION("DRM TYPEC DP HPD BRIDGE");
+MODULE_LICENSE("GPL");
-- 
2.51.1

Hi,

I don't know what's going on here - this series is the 12th?
In any case, you need to fix this..

> diff --git a/drivers/gpu/drm/bridge/aux-hpd-typec-dp-bridge.c b/drivers/gpu/drm/bridge/aux-hpd-typec-dp-bridge.c
> new file mode 100644
> index 000000000000..94be3d5f69e9
> --- /dev/null
> +++ b/drivers/gpu/drm/bridge/aux-hpd-typec-dp-bridge.c
> @@ -0,0 +1,51 @@
> +// SPDX-License-Identifier: GPL-2.0+
> +#include <linux/of.h>
> +#include <linux/usb/typec_altmode.h>
> +#include <linux/usb/typec_dp.h>
> +
> +#include <drm/bridge/aux-bridge.h>
> +
> +static int drm_typec_bus_event(struct notifier_block *nb,
> +			       unsigned long action, void *data)
> +{
> +	struct device *dev = (struct device *)data;
> +	struct typec_altmode *alt = to_typec_altmode(dev);
> +
> +	if (action != BUS_NOTIFY_ADD_DEVICE)
> +		goto done;
> +
> +	if (is_typec_partner_altmode(&alt->dev) || alt->svid != USB_TYPEC_DP_SID)
> +		goto done;

That's still not enough because of the plug altmodes. You need to
check that it's a port altmode:

        if (is_typec_port_altmode(&alt->dev) && alt->svid == USB_TYPEC_DP_SID)
        	drm_dp_hpd_bridge_register(alt->dev.parent->parent,
        				   to_of_node(alt->dev.parent->fwnode));

> +	/*
> +	 * alt->dev.parent->parent : USB-C controller device
> +	 * alt->dev.parent         : USB-C connector device
> +	 */
> +	drm_dp_hpd_bridge_register(alt->dev.parent->parent,
> +				   to_of_node(alt->dev.parent->fwnode));
> +
> +done:
> +	return NOTIFY_OK;
> +}
> +
> +static struct notifier_block drm_typec_event_nb = {
> +	.notifier_call = drm_typec_bus_event,
> +};
> +
> +static void drm_aux_hpd_typec_dp_bridge_module_exit(void)
> +{
> +	bus_unregister_notifier(&typec_bus, &drm_typec_event_nb);
> +}
> +
> +static int __init drm_aux_hpd_typec_dp_bridge_module_init(void)
> +{
> +	bus_register_notifier(&typec_bus, &drm_typec_event_nb);
> +
> +	return 0;
> +}
> +
> +module_init(drm_aux_hpd_typec_dp_bridge_module_init);
> +module_exit(drm_aux_hpd_typec_dp_bridge_module_exit);
> +
> +MODULE_DESCRIPTION("DRM TYPEC DP HPD BRIDGE");
> +MODULE_LICENSE("GPL");

thanks,

-- 
heikki

Hi Heikki,

On 12/4/2025 9:40 PM, Heikki Krogerus wrote:
> Hi,
> 
> I don't know what's going on here - this series is the 12th?
> In any case, you need to fix this..
> 

It is 11th. Patch 1 was missing the Signed-off-by line, so I've resent
it. Sorry for the confusion.

>> diff --git a/drivers/gpu/drm/bridge/aux-hpd-typec-dp-bridge.c b/drivers/gpu/drm/bridge/aux-hpd-typec-dp-bridge.c
>> new file mode 100644
>> index 000000000000..94be3d5f69e9
>> --- /dev/null
>> +++ b/drivers/gpu/drm/bridge/aux-hpd-typec-dp-bridge.c
>> @@ -0,0 +1,51 @@
>> +// SPDX-License-Identifier: GPL-2.0+
>> +#include <linux/of.h>
>> +#include <linux/usb/typec_altmode.h>
>> +#include <linux/usb/typec_dp.h>
>> +
>> +#include <drm/bridge/aux-bridge.h>
>> +
>> +static int drm_typec_bus_event(struct notifier_block *nb,
>> +			       unsigned long action, void *data)
>> +{
>> +	struct device *dev = (struct device *)data;
>> +	struct typec_altmode *alt = to_typec_altmode(dev);
>> +
>> +	if (action != BUS_NOTIFY_ADD_DEVICE)
>> +		goto done;
>> +
>> +	if (is_typec_partner_altmode(&alt->dev) || alt->svid != USB_TYPEC_DP_SID)
>> +		goto done;
> 
> That's still not enough because of the plug altmodes. You need to
> check that it's a port altmode:
> 
>         if (is_typec_port_altmode(&alt->dev) && alt->svid == USB_TYPEC_DP_SID)
>         	drm_dp_hpd_bridge_register(alt->dev.parent->parent,
>         				   to_of_node(alt->dev.parent->fwnode));
>

Oh, it is. Will fix in v12. Thank you.

>> +	/*
>> +	 * alt->dev.parent->parent : USB-C controller device
>> +	 * alt->dev.parent         : USB-C connector device
>> +	 */
>> +	drm_dp_hpd_bridge_register(alt->dev.parent->parent,
>> +				   to_of_node(alt->dev.parent->fwnode));
>> +
>> +done:
>> +	return NOTIFY_OK;
>> +}
>> +
>> +static struct notifier_block drm_typec_event_nb = {
>> +	.notifier_call = drm_typec_bus_event,
>> +};
>> +
>> +static void drm_aux_hpd_typec_dp_bridge_module_exit(void)
>> +{
>> +	bus_unregister_notifier(&typec_bus, &drm_typec_event_nb);
>> +}
>> +
>> +static int __init drm_aux_hpd_typec_dp_bridge_module_init(void)
>> +{
>> +	bus_register_notifier(&typec_bus, &drm_typec_event_nb);
>> +
>> +	return 0;
>> +}
>> +
>> +module_init(drm_aux_hpd_typec_dp_bridge_module_init);
>> +module_exit(drm_aux_hpd_typec_dp_bridge_module_exit);
>> +
>> +MODULE_DESCRIPTION("DRM TYPEC DP HPD BRIDGE");
>> +MODULE_LICENSE("GPL");
> 
> thanks,
> 

-- 
Best, 
Chaoyi

Fri, Dec 05, 2025 at 10:26:20AM +0800, Chaoyi Chen kirjoitti:
> Hi Heikki,
> 
> On 12/4/2025 9:40 PM, Heikki Krogerus wrote:
> > Hi,
> > 
> > I don't know what's going on here - this series is the 12th?
> > In any case, you need to fix this..
> > 
> 
> It is 11th. Patch 1 was missing the Signed-off-by line, so I've resent
> it. Sorry for the confusion.

That's a change too, i.e. this is v12.

> >> diff --git a/drivers/gpu/drm/bridge/aux-hpd-typec-dp-bridge.c b/drivers/gpu/drm/bridge/aux-hpd-typec-dp-bridge.c
> >> new file mode 100644
> >> index 000000000000..94be3d5f69e9
> >> --- /dev/null
> >> +++ b/drivers/gpu/drm/bridge/aux-hpd-typec-dp-bridge.c
> >> @@ -0,0 +1,51 @@
> >> +// SPDX-License-Identifier: GPL-2.0+
> >> +#include <linux/of.h>
> >> +#include <linux/usb/typec_altmode.h>
> >> +#include <linux/usb/typec_dp.h>
> >> +
> >> +#include <drm/bridge/aux-bridge.h>
> >> +
> >> +static int drm_typec_bus_event(struct notifier_block *nb,
> >> +			       unsigned long action, void *data)
> >> +{
> >> +	struct device *dev = (struct device *)data;
> >> +	struct typec_altmode *alt = to_typec_altmode(dev);
> >> +
> >> +	if (action != BUS_NOTIFY_ADD_DEVICE)
> >> +		goto done;
> >> +
> >> +	if (is_typec_partner_altmode(&alt->dev) || alt->svid != USB_TYPEC_DP_SID)
> >> +		goto done;
> > 
> > That's still not enough because of the plug altmodes. You need to
> > check that it's a port altmode:
> > 
> >         if (is_typec_port_altmode(&alt->dev) && alt->svid == USB_TYPEC_DP_SID)
> >         	drm_dp_hpd_bridge_register(alt->dev.parent->parent,
> >         				   to_of_node(alt->dev.parent->fwnode));
> >
> 
> Oh, it is. Will fix in v12. Thank you.

v13. Don't forget to update changelog.

thanks,

-- 
heikki